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BAM Ritchies

Case Study: Upper Rivington Reservoir Grouting

Client: United Utilities

Location: Upper Rivington Chorley

Date: 2011 - 2012

Upper Rivington Reservoir is situated centrally in the Rivington chain of reservoirs, on the West Pennine Moors in Lancashire, England between Rivington and Anglezarke, outside Chorley.

The engineer for the Rivington reservoirs was Thomas Hawksley and construction took place between 1852 and 1857. The two dams of the Upper Rivington reservoir are the 267 metre Horrobin Embankment that separates it from the lower reservoir and carries a road into the village from the west, and the 332 metre long, 12.2 metre high Yarrow Embankment. The Upper Rivington Resevoir has an impounded area of 26 acres and holds about 178 million gallons of water. It is owned and managed by United Utilities and provides fresh water in the Lancashire region and Liverpool. The dam is an earth dam with a clay core.

To ensure the water tightness of the dam, a contract was awarded to BAM Ritchies to grout the fissured rock at its interface with the core.

The aim of the works was to create a grout curtain at the base of the clay core to prevent groundwater eroding the clay at rock head. Tubes-à-manchette’s (TAMs) were used to allow multiple injections at discreet zones at depth. A Jean Lutz grouting system was used to accurately track the volume and pressure of grout being injected into the tubes-à-manchette.

An initial Ground investigation was followed by the main geotechnical injection grouting works.

Initially 250 TAM holes were scheduled split equally both upstream and downstream of the clay core of the reservoir dam. However whilst drilling works were undertaken, a void was identified, which will require further treatment. As the void was found at the furthest extent of the scheduled works additional coring works were carried out to prove the presence of a bedrock of mudstone. This was not the case and a further 224 holes were instructed to be carried out using the same method as the original works. A total of 474 TAM holes were drilled. There were also 10 number raking holes drilled on the embankment at the spillway.

There were some initial high grout takes on during the tubes-à-manchettes installation. The initial phase of works used a total of 191,945kg of grout the additional works used a total of 71,604kg of grout giving an overall total of 254,281kg of grout

The work was undertaken for United Utilities as part of their asset management programme.